Python的SIGPIPE訊號

Have you ever seen a socket.error: [Errno 32] Broken pipe message when running a Python Web server and wondered what that means?

The rule is that when a process tries to write to a socket that has already received an RST packet, the SIGPIPE signal is sent to that process which causes the Broken pipe socket.error exception.

Here are two scenarios that you can try that cause SIGPIPE signal to be fired.

1. Server may send an RST packet to a client to abort the socket connection but the client ignores the packet and continues to write to the socket.

To test that behavior. install Cynic, run it

CODE:

01.$ cynic
02.INFO     [2012-06-08 05:06:37,040] server: Starting 'HTTPHtmlResponse'   on port 2000
03.INFO     [2012-06-08 05:06:37,040] server: Starting 'HTTPJsonResponse'   on port 2001
04.INFO     [2012-06-08 05:06:37,040] server: Starting 'HTTPNoBodyResponse' on port 2002
05.INFO     [2012-06-08 05:06:37,040] server: Starting 'HTTPSlowResponse'   on port 2003
06.INFO     [2012-06-08 05:06:37,040] server: Starting 'RSTResponse'        on port 2020
07.INFO     [2012-06-08 05:06:37,040] server: Starting 'RandomDataResponse' on port 2021
08.INFO     [2012-06-08 05:06:37,040] server: Starting 'NoResponse'         on port 2022
09.INFO     [2012-06-08 05:06:37,041] server: Starting 'LogRecordHandler'   on port /tmp/_cynic.sockand then run the client1.py:

CODE:

01.import socket
02.
03.# connect to Cynic's RSTResponse service on port 2020
04.s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
05.s.connect(('', 2020))
06.
07.# first read gets an RST packet
08.try:
09.s.recv(1024)
10.except socket.error as e:
11.print e
12.print
13.
14.# write after getting the RST causes SIGPIPE signal
15.# to be sent to this process which causes a socket.error
16.# exception
17.s.send('hello')

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